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Study on the Effects and Safety of JR-141 and Idursulfase for Patients with Hunter Syndrome

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What is this trial about?

A plain-language summary of the goals, design and what participants do

This clinical trial is focused on studying a rare genetic disorder called Hunter Syndrome, also known as Mucopolysaccharidosis type II. This condition affects the body's ability to break down certain complex sugars, leading to a variety of health issues. The study is testing a new treatment called JR-141, which is a type of medication designed to help manage the symptoms of Hunter Syndrome. The trial will also compare JR-141 with another treatment known as Elaprase, which is already used for this condition.

The purpose of the study is to evaluate how effective and safe JR-141 is for patients with Hunter Syndrome. Participants in the study will receive either JR-141 or Elaprase, and some may receive a placebo. The study will last for about two years, during which participants will have regular check-ups and assessments to monitor their health and the effects of the treatment. These assessments will include tests to measure changes in symptoms and overall health, as well as regular monitoring for any side effects.

Throughout the study, participants will undergo various evaluations to track their progress. These evaluations will include cognitive tests to assess brain function, as well as physical tests to measure changes in liver and spleen size, walking ability, and lung function. The study aims to provide valuable information on how JR-141 can help manage the symptoms of Hunter Syndrome and improve the quality of life for those affected by this condition.

The research process

The trial runs in 6 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Joining the study

    Upon joining the study, the patient or their legal representative signs a consent form. This form confirms understanding and agreement to participate in the study.

  2. Step 2

    Initial assessment

    The patient undergoes an initial assessment to confirm eligibility. This includes tests to verify a diagnosis of Mucopolysaccharidosis type II, also known as Hunter Syndrome.

  3. Step 3

    Treatment administration

    The patient receives treatment with JR-141 or idursulfase. These are administered as a solution for infusion, which means they are given through a vein.

    The frequency and dosage of the treatment are determined by the study protocol and the patient's specific needs.

  4. Step 4

    Ongoing assessments

    Throughout the study, the patient undergoes regular assessments to monitor the effects of the treatment. These include cognitive tests, physical examinations, and laboratory tests.

    The study measures changes in cognitive abilities, liver and spleen size, and physical endurance, among other factors.

  5. Step 5

    Safety monitoring

    The patient's safety is closely monitored. This includes checking for any adverse reactions to the treatment and conducting regular health checks.

  6. Step 6

    Study completion

    The study is expected to conclude by the end of 2026. At this point, final assessments are conducted to evaluate the overall effects of the treatment.

Who can join the trial?

14 criteria

  • The patient must voluntarily sign a written consent form approved by an ethics committee. If the patient is under 18 years old (or under 16 in the UK) or cannot give consent due to intellectual disability, a legal representative, like a parent or guardian, can sign on their behalf. If possible, the patient should also give their agreement to participate.
  • The patient must have a confirmed diagnosis of **Mucopolysaccharidosis type II (MPS II)**, also known as **Hunter Syndrome**. This is confirmed by:
    • Low activity of the **IDS enzyme** in blood cells, plasma, or skin cells, defined as 10% or less of the normal range.
    • A documented change in the **IDS gene**.
    • Increased levels of certain substances in urine or symptoms like bone problems, facial changes, heart valve issues, developmental delays, lung problems, hernias, spine curvature, joint stiffness, or carpal tunnel syndrome.
    • The patient can either be new to treatment or have been on stable **enzyme replacement therapy (ERT)** with a drug called **idursulfase** for more than 12 weeks before starting the study treatment.
    • For **Cohort A**:
      • Patients aged 36-42 months must have a low score on a cognitive test called **BSID-III**.
      • Patients aged 43-71 months must have either a low development score on the **BSID-III** or a low score on a nonverbal test called **KABC-II** if they can take it.
      • Patients aged 30-35 months with severe symptoms must have specific changes in the **IDS gene** or high levels of certain substances in the spinal fluid.
      • For **Cohort B**:
        • Patients must be 6 years or older.
        • They must have an **IQ** of 70 or higher on a test like the **Wechsler test**.
        • The test must be available in the patient's country.
        • Patients must show certain deficiencies on tests measuring attention or memory.
        • Patients or their female partners who can have children must agree to use effective birth control during the study and for a period after the study ends.
        • If the patient has hearing loss and uses hearing aids, they should use them consistently, especially during cognitive testing.

Who cannot join the trial?

5 criteria

  • Patients who have a medical condition other than **Mucopolysaccharidosis type II** or **Hunter Syndrome**.
  • Patients who are not within the specified age range for the study.
  • Patients who are not part of the specified clinical trial group.
  • Patients who are not male or female, as both genders are included in the study.
  • Patients who are not considered part of a vulnerable population, as this study includes such groups.
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Investigated drugs

JR-141 is a medication being studied for its effects on patients with Mucopolysaccharidosis Type II, also known as Hunter Syndrome. This medication is being tested to see how well it works on symptoms affecting the central nervous system and the body. The study also aims to understand how safe JR-141 is for patients and how the body processes the medication.

What is already known about the treatment

JR-141 – JR-141 is administered through intravenous infusion, allowing the medication to be delivered directly into the bloodstream. It is currently being studied in clinical trials, specifically in a Phase III study, to assess its effectiveness and safety for patients with Mucopolysaccharidosis type II, also known as Hunter Syndrome. The main therapeutic indication for JR-141 is to address both central nervous system and somatic symptoms associated with this condition. At the molecular level, JR-141 works by delivering a modified enzyme that can cross the blood-brain barrier, aiming to replace the deficient enzyme in patients with Hunter Syndrome. It is classified pharmacologically as an enzyme replacement therapy.

Investigated diseases

Mucopolysaccharidosis Type II – This is a rare genetic disorder caused by a deficiency of the enzyme iduronate-2-sulfatase. It leads to the accumulation of glycosaminoglycans in the body's cells, which can cause a variety of symptoms. These symptoms often include developmental delays, distinctive facial features, and joint stiffness. Over time, individuals may experience progressive physical and neurological challenges. The disease primarily affects males and can vary in severity. It is also known as Hunter Syndrome.
Trial detailsLast updated 2 Oct 2026
Age18+ yearsPhasePhase IIITrial ID2024-512289-33-00Protocol codeJR-141-GS31Estimated enrolment80 patientsSponsorJcr Pharmaceuticals Co. Ltd.

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Legal notice · Published by CTIN POLAND sp. z o.o., ul. rtm. Witolda Pileckiego 67/109, 02-781 Warsaw, Poland · KRS 0001111334 · REGON 528919042 · NIP 9512598637

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On this site, “treatment” means an investigational medicine being studied in a clinical trial. Its safety and efficacy for the use being studied have not yet been confirmed, some participants may receive a placebo or a comparator medicine, and taking part does not guarantee any health benefit. The decision to take part is made by the doctor at the research site. This site is for information only and does not replace medical advice.

This service is not affiliated with the European Commission, the EMA, or the official CTIS system. Most information comes from publicly available international clinical-trial registries, supplemented by data from academic sites, national regulators and commercial sponsors. On this site, “treatment” and “therapy” mean a medicine being tested in a clinical trial. Its safety and effectiveness in the use being studied are not yet confirmed, some participants may receive a placebo or a comparator, and taking part does not guarantee a health benefit. The doctor at the research site decides who can take part. This site provides information, not medical advice. Certain content and visual elements on this website have been generated or enhanced using artificial intelligence (AI).